Re: Some highmem pages still in use after shrink_all_memory()?

From: Nigel Cunningham
Date: Mon Mar 08 2004 - 02:47:05 EST


On Mon, 2004-03-08 at 19:36, Andy Isaacson wrote:
> Note that there are some applications for which it is a *bug* if an
> mlocked page gets written out to magnetic media. (gpg, for example.)
> I imagine that they'd rather lose the mapping and get a page fault on
> the next reference (which they can then fix up with a new mmap and
> mlock) than have precious key material written to disk.

For such an application, we'd have to provide a mechanism to allow an
application to set/clear a page's Nosave flag. We'd probably also want
to be able to notify user space that a suspend cycle has just occurred
and the page contents are invalid.

> However, I don't see how to implement a cryptographically secure swsusp.

It would be possible with Suspend2 - one could implement a backend (page
transformer or writer) that implemented encryption and required the user
to enter a passphrase at resume time.

> (The importance of this behavior is obviously dependent on your threat
> model. Perhaps the Sufficiently Paranoid gpg users will simply need to
> avoid using swsusp.)

Yes. Or close all gpg apps before suspending?


Nigel Cunningham
C/- Westminster Presbyterian Church Belconnen
61 Templeton Street, Cook, ACT 2614.
+61 (2) 6251 7727(wk); +61 (2) 6253 0250 (home)

Evolution (n): A hypothetical process whereby infinitely improbable events occur
with alarming frequency, order arises from chaos, and no one is given credit.

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